RJ Ralls, Solid Fuel Services, Wood Burning Stoves

Fuel Types For Stoves

Burning the correct fuel on your appliance will help you get the most efficient use from it. It is important to check that your liner/chimney is suitable for the type of fuel you are using. Using smokeless fuels on the wrong type of liner will dramatically decrease the life of the liner due to increased corrosion. Using the correct fuel will also reduce the amount of soot or tar that builds up and will decrease the risk of a chimney fire.

Using wood as a fuel

Wood is an excellent fuel. It is plentiful, renewable, and nearly carbon neutral. The use of wood however is not well understood, people are unaware of how to get the best from there stove/open fire. Most people would say that they know how to burn a few logs but often there are very important factors which are overlooked.

One is that wood is often not burned in an efficient way, in other words it is not burned at a high enough temperature. Most of what is burning when using wood are voc’s (volatile hydrocarbon compounds). These take the form of tars, creosote etc and constitute about 70-80% of the available energy and are an excellent fuel.

However if the stove does not get up to a hot enough temperature its these voc’s that can cause a problem. These voc’s must first be turned in to a gas before they can burn. If the fire is not hot enough, these vapours are still given off but are not completely burned in the stove and make there way in to the chimney/flue.

It is then that some of these tars cool down and condense and immediately solidify and form tarry deposits on the inside of your chimney/flue which your chimney sweep will try and remove. Not all tars will condense and stick to the sides of the chimney /flue wall, a great deal will be emitted from the top of the stack and this is a serious air pollutant. You will also be losing a lot of available fuel that could of been turned into heat.

How to burn wood efficiently

The moisture content in wood is key for efficient burning, any moisture in wood must be vaporised first before the volatile tars are burned. Trying to burn wood with a high moisture content is a waste of money, energy and can have a serious impact when it comes to chimney fires not to mention that it is bad for the environment.

We recommend burning split seasoned wood with a moisture content of around 20% or less, kiln dried wood is also fine as are manufactured briquettes but be careful with the latter as i have experienced consumers burning through multi-fuel stove grates with these due to how hot they burn. If your wood is wet, your stove won’t get up to a high enough temperature to achieve efficient combustion and lots of un burnt tars enter the chimney cooling down and sticking to the sides of the chimney/flue walls.

All this adds up to increased chances of a chimney fire and pollution to the environment. Not good. Chimneys must also be efficient, it must exert a consistent draw/pull throughout its length and be the right size (cross section). Many stoves are fitted to chimneys that are to big and cold, and even the most efficient stove will not reach its potential without the right chimney above it. Another factor to consider thats just as important is how you operate your stove.

Lack of understanding regarding correct operation of there stove is probably the biggest culprit when it comes to inefficient burning leading to tar creosote problems in there chimney/flue. If the air controls are shut down below a given level, the operating temperature drops and unburnt tars enter the chimney again.

Many consumers like to slumber burn or overnight burn there stove, we don’t recommend this for the reasons we have given above but if you do make sure that you burn your stove at a hot temperature during the day and have your chimney sweep, sweep your chimney at regular intervals. Its a good idea to get your stove installer or your chimney sweep to run through the operation of your stove to make sure your getting it right.

Also many chimney sweeps carry a moisture meter with them, a handy little device that has four sharp prongs that is stuck into a piece of split wood and will give a digital reading on the moisture content, for those of you wishing to do this yourself you can purchase moisture meters at most stove/fireplace shops, or find one online.

Storing/seasoning your wood

You can easily dry logs through correct storage. A well ventilated log store with open sides and a roof is the best way to achieve this, open sides will help air circulate around your logs and the roof will help keep the rainwater out.

It’s of great importance when drying logs that your log store is well ventilated and can keep as much rainwater out as possible. Its best to split your logs before stacking them in your log store, splitting them greatly increases the surface area of each piece so it will dry much faster. It is difficult to say how quickly split logs will season, as so much relies on air humidity and storage, I’ve known it take anything from a few months to a couple of years.

An accurate way to check would be to get yourself a good moisture meter to test the moisture content of any log. Remember, split logs with a moisture content of around 20% or less is ideal, with this in mind try to think ahead and prepare early.

Smokeless fuel and coal

The most traditional fuel for open fires is housecoal and is available in various sizes. Traditional housecoal comes from mines in britain, but also from colombia and indonesia. Its usually sold by the name of the colliery or by the grade-1, 2 and 3 or a, b and c, 1 and a being the best quality. Smokeless fuel can be divided into two categories, Natural smokeless fuel and manufactured smokeless fuel.

Anthracite is a natural smokeless fuel and is still mined in south wales, coalite and phurnaicite are examples of manufactured smokeless fuels. Many different processes will be used to manufacture a smokeless fuel, but the majority of these are based on reducing the volatile content, pulverising, curing and binding the coal/anthracite into a briquette.

Many people are now choosing to use the latest smokeless fuels instead of coal. For some it could be that they live in a smoke control area, or that smokeless fuels are much kinder to the environment, for others that it consistently gives out more heat and can last up to 40% longer than coal. Burning premium smokeless fuels will also work out cheaper over the course of a year than burning ordinary house coal.

If you take Homefire smokeless coal for example, heating efficiencies on an open fire rise to 37% as opposed to 28% using normal house coal, and on a stove these figures will dramatically leap up. All in all you get more heat output to the room and less being wasted up the chimney, coupled with the fact Homefire burns 40% longer than house coal means your spending less money to create your required heat.

Getting the best from your solid fuel appliance

Remove the ash from the ash pan regularly, don’t allow the ash to rise to the grate bars-they will burn away

When burning wood for fuel always burn the wood on a bed of ash. Wood burns much better in its own ash.

Use the riddling device and a poker to clear ash (except when burning wood) and clinker that collects above the grate. The appliance will not run efficiently if the grate is clogged.

Dont open the bottom ash door and leave the main door closed. The intensity of the fire could damage the stove/grate.

The throat plate or baffle plate should be lowered from the top of the stove and cleaned of any ash or chimney soot

Do not burn household waste or papers and old bills

Have your stove checked for wear on rope seals, gaskets, firebricks and baffles etc and replace when nescercery

Have the chimney swept regularly

Smoke control legislation

A number of consumers live in smoke control areas and therefore have to comply with the clean air act. Its an offence to cause smoke from a chimney in a smoke control area. you should use only an authorised smokeless free fuel. There is however an exception, if the appliance is DEFRA approved you can burn wood or housecoal, full details of DEFRA approved appliances are available from the Solid Fuel Association.